In video games? For me (that Pac Man clone boss in the Gather Kirby thread inspired this discussion), here are some I think have no redeeming qualities at all:
Biokinton (Super Mario Land)
Self explanatory. He's a cloud, with eyes, that shoots flying pigeons. I hope the designer didn't get paid for the artwork, because it's certainly not something that required a lot of time and effort.
2. The eyeball bosses in A Link to the Past
Mentioned it before, but dear God, I don't know how the designers could ever get away with making three bosses that were near identical for one SNES era game. True, they're not technically palette swaps, but that doesn't a lot of work, drawing eyeballs and putting them in various patterns.
3. This Pac Man style boss from Gather Kirby 3DS
Bottom right of page one. Basically, he's a wheel with circles inside, with a slice cut out and a face drawn on. I know Pac Man is an iconic character and all, but why make a rip off this late? It seems like the work of an incredibly lazy designer/artist to be honest, especially in a series known for quite complicated and cool looking bosses:
Worse stilt, it's a 3DS game. So you've got the power of a Gamecube with full 3D, and you make an Atari era boss design in a game for it.
4. Many Yoshi's Island DS bosses
True, Salvo the Slime in the original looked a bit lame and Cloud N Candy was awful, but at least they had a sort of quality to them. Or just some kind of detail. On the other hand, at least two Yoshi's Island bosses must have been thrown together at the last minute by a lazy artist/designer catching the bus, while or two more have so little personality and style they're totally forgettable.
The bad:
What is that thing on the top screen? It's a really easy boss too, so it's a lame design and an even worse boss battle.
Six Face Sal is a living WHEEL. Of faces which shoot explosives. No, it makes no sense in game either, especially when Kamek decided to transform an inanimate object.
As for the less lame:
Hector the Reflector had a neat boss battle, but no design as to speak of.
This boss is not just poorly designed, but has no precedent for existing, there are literally no enemies like it in the game, and you don't even see the creature before Kamek transforms it.
So, what boss designs do you think look the worst?
Biokinton (Super Mario Land)
Self explanatory. He's a cloud, with eyes, that shoots flying pigeons. I hope the designer didn't get paid for the artwork, because it's certainly not something that required a lot of time and effort.

2. The eyeball bosses in A Link to the Past
Mentioned it before, but dear God, I don't know how the designers could ever get away with making three bosses that were near identical for one SNES era game. True, they're not technically palette swaps, but that doesn't a lot of work, drawing eyeballs and putting them in various patterns.
3. This Pac Man style boss from Gather Kirby 3DS

Bottom right of page one. Basically, he's a wheel with circles inside, with a slice cut out and a face drawn on. I know Pac Man is an iconic character and all, but why make a rip off this late? It seems like the work of an incredibly lazy designer/artist to be honest, especially in a series known for quite complicated and cool looking bosses:


Worse stilt, it's a 3DS game. So you've got the power of a Gamecube with full 3D, and you make an Atari era boss design in a game for it.
4. Many Yoshi's Island DS bosses
True, Salvo the Slime in the original looked a bit lame and Cloud N Candy was awful, but at least they had a sort of quality to them. Or just some kind of detail. On the other hand, at least two Yoshi's Island bosses must have been thrown together at the last minute by a lazy artist/designer catching the bus, while or two more have so little personality and style they're totally forgettable.
The bad:

What is that thing on the top screen? It's a really easy boss too, so it's a lame design and an even worse boss battle.

Six Face Sal is a living WHEEL. Of faces which shoot explosives. No, it makes no sense in game either, especially when Kamek decided to transform an inanimate object.
As for the less lame:

Hector the Reflector had a neat boss battle, but no design as to speak of.

This boss is not just poorly designed, but has no precedent for existing, there are literally no enemies like it in the game, and you don't even see the creature before Kamek transforms it.
So, what boss designs do you think look the worst?